BackgroundCancer cachexia is largely irreversible, at least via nutritional means, and responsible for 20–40% of cancer‐related deaths. Therefore, preventive measures are of primary importance; however, little is known about muscle perturbations prior to onset of cachexia. Cancer cachexia is associated with mitochondrial degeneration; yet, it remains to be determined if mitochondrial degeneration precedes muscle wasting in cancer cachexia. Therefore, our purpose was to determine if mitochondrial degeneration precedes cancer‐induced muscle wasting in tumour‐bearing mice.MethodsFirst, weight‐stable (MinStable) and cachectic (MinCC) Apc Min/+ mice were compared with C57Bl6/J controls for mRNA contents of mitochondrial quality regulators in quadriceps muscle. Next, Lewis lung carcinoma (LLC) cells or PBS (control) were injected into the hind flank of C57Bl6/J mice at 8 week age, and tumour allowed to develop for 1, 2, 3, or 4 weeks to examine time course of cachectic development. Succinate dehydrogenase stain was used to measure oxidative phenotype in tibialis anterior muscle. Mitochondrial quality and function were assessed using the reporter MitoTimer by transfection to flexor digitorum brevis and mitochondrial function/ROS emission in permeabilized adult myofibres from plantaris. RT‐qPCR and immunoblot measured the expression of mitochondrial quality control and antioxidant proteins. Data were analysed by one‐way ANOVA with Student–Newman–Kuels post hoc test.ResultsMinStable mice displayed ~50% lower Pgc‐1α, Pparα, and Mfn2 compared with C57Bl6/J controls, whereas MinCC exhibited 10‐fold greater Bnip3 content compared with C57Bl6/J controls. In LLC, cachectic muscle loss was evident only at 4 weeks post‐tumour implantation. Oxidative capacity and mitochondrial content decreased by ~40% 4 weeks post‐tumour implantation. Mitochondrial function decreased by ~25% by 3 weeks after tumour implantation. Mitochondrial degeneration was evident by 2 week LLC compared with PBS control, indicated by MitoTimer red/green ratio and number of pure red puncta. Mitochondrial ROS production was elevated by ~50 to ~100% when compared with PBS at 1–3 weeks post‐tumour implantation. Mitochondrial quality control was dysregulated throughout the progression of cancer cachexia in tumour‐bearing mice. In contrast, antioxidant proteins were not altered in cachectic muscle wasting.ConclusionsFunctional mitochondrial degeneration is evident in LLC tumour‐bearing mice prior to muscle atrophy. Contents of mitochondrial quality regulators across Apc Min/+ and LLC mice suggest impaired mitochondrial quality control as a commonality among pre‐clinical models of cancer cachexia. Our data provide novel evidence for impaired mitochondrial health prior to cachectic muscle loss and provide a potential therapeutic target to prevent cancer cachexia.

Muscle atrophy is a hallmark of cancer cachexia resulting in impaired function and quality of life and cachexia is the immediate cause of death for 20-40% of cancer patients. Multiple microRNAs (miRNAs) have been identified as being involved in muscle development and atrophy; however, less is known specifically on miRNAs in cancer cachexia. The purpose of this investigation was to examine the miRNA profile of skeletal muscle atrophy induced by cancer cachexia to uncover potential miRNAs involved with this catabolic condition. Phosphate-buffered saline (PBS) or Lewis lung carcinoma cells (LLC) were injected into C57BL/6J mice at 8 wk of age. LLC animals were allowed to develop tumors for 4 wk to induce cachexia. Tibialis anterior muscles were extracted and processed to isolate small RNAs, which were used for miRNA sequencing. Sequencing results were assembled with mature miRNAs, and functions of miRNAs were analyzed by Ingenuity Pathway Analysis. LLC animals developed tumors that contributed to significantly smaller tibialis anterior muscles (18.5%) and muscle cross-sectional area (40%) compared with PBS. We found 371 miRNAs to be present in the muscle above background levels. Of these, nine miRNAs were found to be differentially expressed. Significantly altered groups of miRNAs were categorized into primary functionalities including cancer, cell-to-cell signaling, and cellular development among others. Gene network analysis predicted specific alterations of factors contributing to muscle size including Akt, FOXO3, and others. These results create a foundation for future research into the sufficiency of targeting these genes to attenuate muscle loss in cancer cachexia.

A renewed emphasis on clinical competence and its assessment has grown out of public concerns about the safety, efficacy, and accountability of health care in the United States. Medical schools and residency training programs are paying increased attention to teaching and evaluating basic clinical skills, stimulated in part by these concerns and the responding initiatives of accrediting, certifying, and licensing bodies. This paper, from the Residency Review Committee for Internal Medicine of the Accreditation Council for Graduate Medical Education, proposes a new outcomes-based accreditation strategy for residency training programs in internal medicine. It shifts residency program accreditation from external audit of educational process to continuous assessment and improvement of trainee clinical competence.

Our findings reveal a novel mechanism suppressing Pgc1α4 gene expression via IL-6-ERK-MAPK and suggest this signalling axis may inhibit Pgc1α4 in some, but not all, (patho)physiological conditions.

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Cancer-cachexia (CC) is a wasting condition directly responsible for 20–40% of cancer-related deaths. The mechanisms controlling development of CC-induced muscle wasting are not fully elucidated. Most investigations focus on the postcachectic state and do not examine progression of the condition. We recently demonstrated mitochondrial degenerations precede muscle wasting in time course progression of CC. However, the extent of muscle perturbations before wasting in CC is unknown. Therefore, we performed global gene expression analysis in CC-induced muscle wasting to enhance understanding of intramuscular perturbations across the development of CC. Lewis lung carcinoma (LLC) was injected into the hind-flank of C57BL6/J mice at 8 wk of age with tumor allowed to develop for 1, 2, 3, or 4 wk and compared with PBS-injected control. Muscle wasting was evident at 4 wk LLC. RNA sequencing of gastrocnemius muscle samples showed widespread alterations in LLC compared with PBS animals with largest differences seen in 4 wk LLC, suggesting extensive transcriptomic alterations concurrent to muscle wasting. Commonly altered pathways included: mitochondrial dysfunction and protein ubiquitination, along with other less studied processes in this condition regulating transcription/translation and cytoskeletal structure. Current findings present novel evidence of transcriptomic shifts and altered cellular pathways in CC-induced muscle wasting.

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